Recently, with the development of technology, portable terminal devices have come to be widely used. Some portable terminal devices provide notifications to users by outputting sound. For example, a mobile phone can notify a user by outputting sound in response to an incoming call request or when an SMS message is received. Furthermore, a mobile phone may notify a user by outputting sound when an alarm time set by a user is reached.
However, in general, the direction in which sound is output is not set appropriately, that is, sound is output in all directions without directionality. Furthermore, the volume of sound output is not suitably set. In this case, other persons can feel disturbed and inconvenienced because the sound with the high volume is coming from other's terminal other than their terminals.
Accordingly, there is a need for a method of appropriately controlling a direction of sound, or a volume of sound, or both.